Handle PydanticUndefined, add tests

libs/langgraph/langgraph/utils/fields.py

@@ -110,7 +110,7 @@ def get_field_default(name: str, type_: Any, schema: Type[Any]) -> Any:
 
 def get_enhanced_type_hints(
     type: Type[Any],
-) -> Generator[tuple[str, Any, Any, Optional[str]], None]:
+) -> Generator[tuple[str, Any, Any, Optional[str]], None, None]:
     """Attempt to extract default values and descriptions from provided type, used for config schema."""
     for name, typ in get_type_hints(type).items():
         default = None
@@ -126,6 +126,12 @@ def get_enhanced_type_hints(
 
                 if hasattr(field, "default") and field.default is not None:
                     default = field.default
+                    if (
+                        hasattr(default, "__class__")
+                        and getattr(default.__class__, "__name__", "")
+                        == "PydanticUndefinedType"
+                    ):
+                        default = None
 
         except (AttributeError, KeyError, TypeError):
             pass

libs/langgraph/tests/test_utils.py

@@ -21,7 +21,11 @@ from typing_extensions import Annotated, NotRequired, Required
 
 from langgraph.graph import END, StateGraph
 from langgraph.graph.graph import CompiledGraph
-from langgraph.utils.fields import _is_optional_type, get_field_default
+from langgraph.utils.fields import (
+    _is_optional_type,
+    get_enhanced_type_hints,
+    get_field_default,
+)
 from langgraph.utils.runnable import is_async_callable, is_async_generator
 
 pytestmark = pytest.mark.anyio
@@ -227,3 +231,57 @@ def test_is_required():
     assert get_field_default("val_12", gcannos["val_12"], MyGrandChildDict) is None
     assert get_field_default("val_9", gcannos["val_9"], MyGrandChildDict) is None
     assert get_field_default("val_13", gcannos["val_13"], MyGrandChildDict) == ...
+
+
+def test_enhanced_type_hints() -> None:
+    from dataclasses import dataclass
+    from typing import Annotated
+
+    from pydantic import BaseModel, Field
+
+    class MyTypedDict(TypedDict):
+        val_1: str
+        val_2: int = 42
+        val_3: str = "default"
+
+    hints = list(get_enhanced_type_hints(MyTypedDict))
+    assert len(hints) == 3
+    assert hints[0] == ("val_1", str, None, None)
+    assert hints[1] == ("val_2", int, 42, None)
+    assert hints[2] == ("val_3", str, "default", None)
+
+    @dataclass
+    class MyDataclass:
+        val_1: str
+        val_2: int = 42
+        val_3: str = "default"
+
+    hints = list(get_enhanced_type_hints(MyDataclass))
+    assert len(hints) == 3
+    assert hints[0] == ("val_1", str, None, None)
+    assert hints[1] == ("val_2", int, 42, None)
+    assert hints[2] == ("val_3", str, "default", None)
+
+    class MyPydanticModel(BaseModel):
+        val_1: str
+        val_2: int = 42
+        val_3: str = Field(default="default", description="A description")
+
+    hints = list(get_enhanced_type_hints(MyPydanticModel))
+    assert len(hints) == 3
+    assert hints[0] == ("val_1", str, None, None)
+    assert hints[1] == ("val_2", int, 42, None)
+    assert hints[2] == ("val_3", str, "default", "A description")
+
+    class MyPydanticModelWithAnnotated(BaseModel):
+        val_1: Annotated[str, Field(description="A description")]
+        val_2: Annotated[int, Field(default=42)]
+        val_3: Annotated[
+            str, Field(default="default", description="Another description")
+        ]
+
+    hints = list(get_enhanced_type_hints(MyPydanticModelWithAnnotated))
+    assert len(hints) == 3
+    assert hints[0] == ("val_1", str, None, "A description")
+    assert hints[1] == ("val_2", int, 42, None)
+    assert hints[2] == ("val_3", str, "default", "Another description")